Autonomic dysreflexic hypertension occurs in up to 80% of spinal cord injury patients with lesions thoracic level 6 or higher. Pharmacologic agents directed at each part of the autonomic dysreflexic circuit were tested for efficacy in a rat model. Guanethidine (15 mg/kg intraperitoneally), alpha-methyl-paratyrosine (20 mg/kg intraperitonally), propranolol (3 mg/kg intraperitonally) and control were each tested on groups of three rats with intrinsic control blood pressure measurements. Results show an increase of 15 +/- 5 mm Hg diastolic pressure in control animals compared with no detectable increase with guanethidine or alpha-methyl-paratyrosine. There was an 11 +/- 2 mm Hg increase in diastolic pressure with propranolol. In conclusion, screening drug trials show that the ganglionic blocking agent, guanethidine, and competitive tyrosine uptake precursor, alpha-methyl-paratyrosine, effectively blocked dysreflexic hypertension, whereas the beta-blocker, propranolol, did not.